* Make "All Pokemon" rules more convenient
Previously, "+All Pokemon" did nothing except override "-All Pokemon",
which switched from a default-allow to default-deny system.
They still do that, but they now also override all previous pokemon
bans/unbans. This makes it easier to replace a banlist/whitelist
from an inherited ruleset without needing to reverse every previous
ban/unban.
This also adds an error if you use `+All Pokemon` in a ruleset where
it doesn't do anything.
Fixes#10772
`no item` is now a fake item meaning "not holding an item", for the
purposes of the team validator. This means that `-no item` will force
all pokemon to carry items.
`all items` no longer includes not holding an item, so `-all items`
will now work as expected.
Also stop enforcing 4 moves limit and 6 pokemon limit in `-Nonstandard`,
for the same reason we stopped enforcing the level 100 limit; any format
that explicitly wants it higher should automatically override it.
`teamLength`, `maxLevel`, `cupLevelLimit`, and `minSourceGen` no longer
exist as properties of `Format`. Instead, they're value rules that
become properties of `RuleTable`, and can be specified as custom rules
and inherited through rulesets like anything else.
See the PR for a full reckoning of changes:
https://github.com/smogon/pokemon-showdown/pull/8267
